Conventionally, as a light source device using an LED, as disclosed in Patent literature 1, there is one that is provided with: a first housing (cover part and board) that contains an LED board mounted with an LED; a second housing (circuit containing part) that contains a drive circuit part; and a retaining post that connects the first and second housings to each other. Also, in order to release heat generated from the LED to outer air, the retaining post is provided with a heat dissipation part.
However, the above-described light source device is adapted to transfer the heat from the LED to the heat dissipation part through the retaining post that connects the first and second housings to each other, and therefore the heat from the LED is transferred not only to the heat dissipation part but also to the second housing. Also, in the case where a temperature of the drive circuit part is higher than that of the LED, heat from the drive circuit part is transferred to the first housing. That is, the above-described light source device has a problem of insufficient thermal isolation between the LED and the drive circuit part.
Also, as disclosed in Patent literature 2, there is one that is provided with: a first housing (plate-like part and cover member) that contains an LED board; a second housing (lower housing) that contains a control circuit; and a third housing (housing) that connects the first and second housings to each other over their side peripheral surfaces. Also, inside the third housing, a heat dissipation member that is thermally joined to the LED board is provided, and the housing is formed with an opening part.
However, the third housing connects the side peripheral surfaces of the first and second housings throughout, and therefore there is a problem of insufficient thermal isolation. Also, the heat dissipation member is provided only on the LED board side, and heat dissipation of the second housing that contains the control circuit is not taken into account at all. Such a configuration causes the control circuit to be thermally influenced, which causes a failure or the like.
In short, these problems are caused by not recognizing a clear issue related to the need for thermal isolation in the first place.
Further, as disclosed in Patent literature 3, there is an LED lamp that is provided with a lamp housing, an LED light source, a heat sink, a control circuit, and a fan. Also, the lamp housing has a containing space, and pluralities of inlets and outlets, and in the containing space thereof, the LED light source, the heat sink, and the control circuit are arranged. Further, in the containing space, the fan is provided, and by the fan, external air flows into the containing space through the inlet, flows between heat dissipation fins of the heat sink, and then flows outward through the outlet. As described, this lamp facilitates heat dissipation from the LED light source by providing the fan in the containing space.
However, the LED light source and the control circuit are fixed to the one lamp housing, and a thermal isolation between the LED light source and the control circuit is insufficient. That is, there is a problem that heat from the LED light source transfers to the control circuit through the lamp housing.